The main objective of the proposed study is to develop an antenatal physical activity intervention to promote engagement in regular leisure physical activity (RLPA). In order to inform the development of the intervention, ethnographic studies will be conducted to better understand what factors facilitate and prevent pregnant women from engaging in RLPA and to what extent these may differ among pregnant women who are first time or veteran mothers and among pregnant women who currently engage in RLPA versus those who do not (i.e. are sedentary or engage in low levels of RLPA). The proposed pilot physical activity intervention will be designed to improve certain personal determinants (i.e. self-efficacy, behavioral skills, and social support). These personal determinants have been suggested to be effective mediators of physical activity. The specific aims of the study are to: 1) conduct ethnographic studies to examine barriers and facilitators to physical activity engagement among pregnant women;2) Develop a manual of procedures to conduct a randomized physical activity pilot intervention to increase antenatal regular leisure physical activity;3) Determine which recruitment strategies based on type (e.g. healthcare provider, community organizations, print advertisements) and setting (e.g. healthcare clinics, hospitals, community organizations) that produce the most effective yield;4) Pilot test methodologies in pregnant women (n=40;20 intervention, 20 control) to provide necessary information (e.g. effect sizes, adherence and attrition rates) to guide future implementation of a large-scale, randomized controlled physical activity intervention trial in the antenatal period. The hypotheses to be tested in the larger RCT trial include 1) women who engage in the physical activity intervention will report greater levels of physical self-efficacy, behavioral skills, and social support, compared to women in the control group;2) women in the intervention group will report an increase in RLPA, decrease in antenatal weight gain, antenatal depression and perceived stress compared to their control counterparts;and 3) engagement in antenatal RLPA will reduce the risk of adverse birth outcomes, postpartum depression and overweight.